Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$196.69	13.321%	$222.8911	$222.89	$222.90	$222.90
Purchase #2	$48.44	6.762%	$51.7155	$51.72	$51.70	$51.70
Purchase #3	$135.25	10.740%	$149.7759	$149.78	$149.80	$149.80
Purchase #4	$59.99	4.488%	$62.6824	$62.68	$62.70	$62.70
Purchase #5	$157.45	6.250%	$167.2906	$167.29	$167.30	$167.30
Purchase #6	$137.42	13.754%	$156.3207	$156.32	$156.30	$156.30
Purchase #7	$177.40	9.312%	$193.9195	$193.92	$193.90	$193.90
7 purchase totals =	$912.64		$1,004.5957	$1,004.60	$1,004.60	$1,004.60